In 1979, Congress directed the Bureau of Reclamation to conduct a feasibility study of the Yakima River Basin Water Enhancement Project. The congressional objectives of the YRBWEP study were to develop a plan that would provide supplemental water for presently irrigated lands, water for new lands within the Yakama Indian Reservation, water for increased instream flows for aquatic life, and a comprehensive plan for efficient management of basin water supplies.

Early in the YRBWEP study process, fish passage problems were indentified as needing immediate early attention and congressional legislation in 1984 authorized YRBWEP Phase 1, which primarily involved rebuilding fish ladders and constructing fish screens on river diversions.

The YRBWEP study proceeded through the 1980s but was not fully completed primarily due to issues and uncertainties associated with the adjudication of the basin surface waters that began in 1978. Consequently, Congress passed legislation in 1994 for what is generally referred to as YRBWEP Phase 2. This legislation provided for significant water conservation and acquisition activities, studies to define the long-term water needs of fish and current irrigators, improvements to the Wapato Irrigation Project, and development of an interim plan for management of basin water supplies.